Support complex data type in ExecuTorch

[iseeyuan]

Currently complex data type is not supported in ExecuTorch runtime. Although the model may be rewritten to real number operations, but it would affect the user's development efficiency.

What is complex data type here?
It's the math number system with real and imaginary parts like c = x * i * y.

It's used in some operations in PyTorch, like RoPE embedding in LLM, or Fourier Transforms (FFT).

[mergennachin]

cc @swolchok - is this supported now?

[swolchok]

supported

that depends on your definition of "supported". can you do more than zero things with a tensor of complex dtype? yes -- you can call abs(). can you do more than one thing? not as far as I know.